We propose to determine the mechanism of motility and chemotaxis in bacteria. There are at least two polypeptides that are important in the determination of flagellar rotation. These are integral membrane proteins and they are the products of the mot A and mot B genes. We have identified these polypeptides and are developing procedures to isolate and purify them in order to determine how they function. The mot proteins transduce the energy of the pH gradient across the bacterial membrane into rotary motion of the flagellar apparatus. We plan to isolate the products of the tsr and the tar genes. These are genes that are required for the cells to respond to chemotactic signals. They code for membrane proteins and they are thought to act as transmembrane signalling elements. We plan to reconstitute membrane protein systems so that we can study the mechanism of action of these polypeptides. This work should give us some insight into the way that energy transduction occurs in biological systems and the mechanisms by which information is transmitted across the membrane.